Application |
PLAXIS 3D |

Version |
PLAXIS 3D |

Date created |
07 November 2011 |

Date modified |
07 November 2011 |

*This is based on the Engineering Example as described in the PLAXIS 3D 2011 Material models manual.*

In PLAXIS 3D plate elements are assumed to be plates with a rectangular cross-section. With some assumptions, the parameters for a material dataset for a sheet pile wall in bending can be calculated.

From the sheet-pile manufacturer, the following properties are known: t (wall thickness), h (total height), A (per m wall width), I_{1}, E_{steel} and γ_{steel}.

The structure is geometrically orthotropic with significant different stiffnesses in horizontal and vertical direction. It is known that the axial stiffness in vertical direction is larger than the effective stiffness in horizontal direction (E_{1} > E_{2}). Moreover, the flexural rigidity against bending over the vertical direction, I1, is much larger than the stiffness against bending over the horizontal direction, I_{2}, (I_{1} >> I_{2} say I_{1} ≈ 20 I_{2} and I_{1} >> I_{12} say I_{1} ≈ 10 I_{12})* ^{++)}*.

Furthermore, it is assumed that the cross section area that is effective against shear deformation over the vertical direction is about 1/3 of the total cross section area, whereas the area that is effective against shear deformation over the horizontal direction is about 1/10 of the total cross section area. Finally, the Poisson's ratio's for sheet pile walls can be assumed zero.

With these assumptions, the situation could be modelled by selecting the model parameters in the following way:

In the attached Microsoft Excel spreadsheet, you can find these equations to determine the sheetpile wall parameters. Due to these assumptions to calculate the bending correctly, the axial stiffness is not correct, resulting in incorrect axial forces. *The usage of this spreadsheet is at own risk. The PLAXIS program Disclaimer applies.*

* ^{++)}* A factor of 20 is used here to move the bending stiffness over the first direction sufficiently small compared to the bending stiffness over the second direction, whilst the matrix condition is still OK. Note that in reality bending stiffness differences in order of 1000 may exist.